If the question you're asking is whether a triple bond is indicated with 2 columns of 3 electrons each or 3 columns of 2 electrons each, then the answer is b.
Single bond- C:C; double bond- C::C; triple bond- C:::C

If the question you're asking is whether a triple bond is indicated with 2 columns of 3 electrons each or 3 columns of 2 electrons each, then the answer is b.
Single bond- C:C; double bond- C::C; triple bond- C:::C

I'm not too sure about that. How are you judging the answer by? I'll give out all the choices now;

a) H:C::C
____. ._. .
b) H:C : C

(the period represents one electron)
c) H.C:::C.H
_____ ..
d) H:C::C

____.__.
e)H:C: C: H
____'__'

According to t!m the answer is c), but that wouldn't make any sense for the electrons shared by the hydrogens and carbons. i think the answer is d)

This is merely a question of representation. What everyone's trying to say, is that the C atoms in ethyne are bonded to each other by a triple bond. How you represent this triple bond doesn't matter terribly, as long as the other person knows what you mean. The standard representation, however, would be either what Dexter has used (common for designating organic compounds) or what The Bob has used (known as Lewis Dot Structures, these are used specifically when solving problems on electronic configurations).

The important thing to learn here, however, is what poolwin has mentioned : that the triple (covalent) bond is the only structure that ensures an octet for C and a duet for the H atom. So, while the representation of the structure is useful for effective communication, understanding the 'why' of the structure is more important.